Passive immunization with human monoclonal antibodies (mAbs) against anthrax could be used by military personnel during warfare or the general public in the event of bioterrorist activity. To establish a foundation for potential clinical testing, we propose to develop and characterize human mAbs in the IgG format against both spores and the protective antigen (PA) of B. anthracis. Key features of the research include our 1) phage-display human scFv libraries, 2) experience in obtaining scFvs against Bacillus spores and various protein antigens, 3) expertise in molecular evolution to enhance scFv affinity, and 4) ability to convert scFvs into the Fab and whole human IgG formats. Our strategy: 1) scFvs will be obtained against spores by biopanning, selection, and characterization; 2) conversion of the best anti-spore scFvs to the Fab format for retesting, and assembly of human IgGs; 3) scFvs will be obtained against PA not only by conventional biopanning, but also by whole-cell biopanning of PA in the active, membrane-associated structure; 4) conversion of the best anti-PA scFvs to the Fab format for in vitro assays, affinity-enhancement and retesting, and assembly of human IgGs; 5) final testing of anti-PA IgGs in vitro for protection against cytotoxicity from exotoxin (PA in combination with lethal factor, LF), and studies of both anti-spore and anti-PA IgGs with regard to macrophage-spore-lgG interactions. We believe all experiments, both established and novel, will provide valuable information about the future potential of passive immunization as a treatment and/or prophylaxis for anthrax. [unreadable] [unreadable]